Oil recovery from fractured reservoirs using in situ and preformed particle gels in micromodel structures

Abstract

Oil extraction often accompanied with relatively large amounts of water production causes several environmental and mechanical problems, particularly in oil-fractured reservoirs. One way to alleviate this problem is to use gels as a blockage agent. In this study, several micromodels with different geometries of fractures including a simple fracture, step fracture, fracture with variable mouth and fracture with a tiny crack were prepared. The amount of oil recovery was measured from these micromodels in the presence or absence of gel. In situ and preformed particle gels (PPGs) were injected into the micromodels to compare their ability in blocking fractures and increasing oil recovery. The BaCl2·2H2O salt solution was used to swell PPGs. The amount of salt concentration was optimized so that PPGs had maximum ability to block fractures. Several PPG concentrations, 1000, 2000, and 3000 ppm, were examined to optimize the amount of PPGs, which have to be injected into the micromodels. Injection flow rate was optimized so that salt water could efficiently sweep the matrix structure. Results showed that both PPG and in situ gels have a considerable effect on decreasing water production and increasing oil extraction. However, PPGs were superior in comparison to in situ gels to increase oil recovery. It was found that increasing salt concentration decreases the swelling percentage of PPGs. The optimum amount of injection flow rate was found to be 0.1 mL/hr for all the prepared micromodels. The optimum concentration of PPGs was different for each micromodel.